The present invention relates generally to radiotelephones and, more particularly, to radiotelephone antennas.
Radiotelephones generally refer to communications terminals which provide a wireless communications link to one or more other communications terminals. Radiotelephones may be used in a variety of different applications, including cellular telephone, land-mobile (e.g., police and fire departments), and satellite communications systems.
Radiotelephones and other communication devices are undergoing miniaturization. Indeed, many of the contemporary radiotelephone models are less than 11-12 centimeters in length. As a result, primary antennas that swivel or pivot from a stored position overlying the keypad or other housing portion of a radiotelephone to a position extending outwardly from the radiotelephone are becoming increasingly attractive to radiotelephone manufacturers. Pivotable primary antennas can achieve good radiation performance when in outwardly extended positions. Unfortunately, these pivotable antennas can be blocked by the body of a user when in a stored position (also known as xe2x80x9cbody shadowingxe2x80x9d). As a result, radiotelephone operation may be difficult when a pivotable antenna is in a stored position.
In addition, when in a stored position, pivotable primary antennas that overlie a keypad or other housing portion of a radiotelephone may be insufficient for paging mode operation. For example, when a radiotelephone with a pivotable primary antenna in a stored position is placed within a user""s shirt pocket, with the pivotable primary antenna facing the user""s body (body shadowing problem), signal reception and radiation may be blocked by the user""s body on one side and portions of the radiotelephone housing on the other side, particularly conductive housing portions.
It would be desirable to enhance the ability of radiotelephones that utilize pivotable primary antennas that overlie a keypad or other housing portion to receive paging signals when the primary antenna is in a stored position.
In view of the above, it is therefore an object of the present invention to enhance the ability of radiotelephones utilizing pivotable primary antennas to receive paging signals when a primary antenna is in a stored position.
It is another object of the present invention to facilitate miniaturization efforts with respect to radiotelephones and other communication devices.
These and other objects of the present invention are provided by antenna systems for electronic devices, such as radiotelephones, wherein a paging antenna is provided to enhance paging mode operation when a pivotable primary antenna is in a stored position. Radiotelephones incorporating a pivotable primary antenna typically utilize a hinge rotatably secured to one end of the radiotelephone housing. A primary antenna having a first radiation axis (i.e., signal vector) is secured to the hinge and rotatable therewith along a predetermined path of rotation from a stored position adjacent the housing to an operating position extending away from the housing. A paging antenna according to the present invention is disposed within the hinge and is electrically connected with the primary antenna. The paging antenna has a second radiation axis (i.e., signal vector) that is orthogonal to the first radiation axis of the primary antenna and is configured to receive paging signals when the primary antenna is in a stored position.
Because paging antennas according to the present invention are located in a position unobstructed by other portions of a radiotelephone housing, a paging signal can be received even when the primary antenna is in a stored position. Paging antennas according to the present invention preferably have a coiled (e.g., helical or conical) configuration that comprises a radiation axis that is orthogonal to the radiation axis of the primary antenna. The paging antenna may operate as a quarter-wave antenna, such that the primary antenna and paging antennas operate independently as quarter-wave antennas in the operating and stored positions. Because the radiation axes of the primary and paging antennas are orthogonal, the vector sum of the primary and paging antenna signal vectors is the input signal to the transceiver. In addition, paging antennas according to the present invention are preferably configured such that an impedance of the primary antenna and paging antenna, in combination, matches an impedance of the transceiver when the primary antenna is in both the stored and operating positions.
Radiotelephones incorporating paging antennas according to the present invention can be advantageous because paging signals can be received even when a primary antenna is in a stored position and a radiotelephone is stored within a user""s pocket. As a result, performance of radiotelephones, particularly paging performance, may be enhanced by the present invention. Furthermore, a paging antenna according to the present invention can combine with a primary antenna for better signal reception when the primary antenna is in both a stored and operating position.